Method for production of cross-lapped structures

ABSTRACT

A method for producing cross lapped structures such as battings from lightweight continuous filament webs utilizing high speed delivery means wherein the lightweight web is traversed across a moving collection means utilizing air currents to aid in the traversal, thereby producing a cross lapped structure.

0 i r I, [I] 151111 States atent n51 3,66,867

Watson 1 any 9, 1972 54] METHOD FOR PRODUCTION OF 3,328,850 7/1967Watson ..19/65 T PED STRUCTURES 3,380,131 4/1968 Gray 19/65 T UX [72]Inventor: George A. Watson, Charlotte, NC FOREIGN PATENTS ORAPPLICATlONS[73] Assignee: Celanese Corporation, New York, NY. 533,780 11/1956Canada ..28/21 [22] Filed May 13 1970 564,370 10/1958 Canada ..28/21[21] AppLNo; 37,416 PrimaryEraminer-Robert R. Mackey A -D.J.D n d h D.Related [1.8. Application Data Home" ewl an Step en Murphy [63]Continuation of Ser, No. 568,877, July 29, 1966, ABSTRACT abandoned.

A method for producing cross lapped structures such as [52] U 8 Cl19/163 28/72 NW battings from lightweight continuous filament websutilizing [51] 25/00D04h 3/02 high speed delivery means wherein thelightweight web is [58] Fie'ld T 160 3 28/1 SM traversed across a movingcollection means utilizing air cur. 28/21 72 rents to aid in thetraversal, thereby producing a cross lapped structure.

[56] References Cited 3 Claims, 24 Drawing Figures PATENTEDHAY '9 I972SHEET 1 [1F 6 PATENTEDW 9 I972 SHEET 2 [1F 6 PATENTEQMAY 9 I972 SHEET 5[1F 6 METHOD FOR PRODUCTION OF CROSS-LAPPED STRUCTURES This applicationis a continuation of application Ser. No. 568,877 filed July 29, 1966,now abandoned.

This invention relates to the production of batting materials andpillows.

One object of this invention is to provide novel, economical, and highlyeffective methods for the cross-lapping of fine webs of substantiallyparallel continuous filaments.

Other objects of this invention will be apparent from the followingdetailed description and claims.

The invention finds its greatest utility in the handling of fine,diaphanous, limp, cohesive spread webs of substantially parallel crimpedcontinuous filaments.

Certain aspects of this invention are illustrated in the accompanyingdrawings, in which FIG. 1 is a schematic perspective view of a portionof a cross-lapping apparatus.

FIG. 2 is a schematic perspective view showing a tow opening andspreading operation for supplying a wide web of crimped, substantiallyparallel continuous filaments to a crosslapping operation.

FIG. 3 is a schematic view in elevation showing a webeutting device atthe exit of a cross-lapping chute.

FIG. 4 is a schematic view in elevation showing the relationship betweenthe traverse of the chute and the width of the cross-lapped batting, andindicating the path of the web leaving the chute.

FIGS. 5, 6, 7 and 8 are schematic views in elevation showing the path ofthe web in relation to the position of the chute at various times duringthe traverse movement of the chute.

FIG. 9 is a view in elevation taken at about the same time as that ofFIG. 6, but at right angles to the latter.

FIG. 10 is a schematic view in elevation showing a crosslappingarrangement like that of FIGS. 1-9, modified by the use of baffles.

FIG. 11 is a schematic view in elevation, taken at right angles to FIG.10.-

FIG. 12 is a schematic view in elevation showing a crosslappingarrangement like that of FIGS. 1-9, modified by the use of certainbaffles overlying the ballooning portion of the web.

FIG. 13 is a schematic view in elevation taken at right angles to FIG.12.

FIGS. 14 and 15 are schematic views in elevation, taken at differenttimes in the traverse cycle and showing an arrangement in which the webis traversed solely by the action of streams of air. I

FIG. 16 is a schematic view in elevation showing a method for formingthe crosslaid web into a rolled batt.

FIGS. 17 and 18 are schematic views in elevation taken at differentstages in a pillow-making operation and showing the formation of a wadof randomly folded material.

FIG. 19 is a cross-sectional view of a rolled cross-lapped batt having acentral wad of randomly folded material.

FIG. 20 is a schematic view in elevation of a modified crosslappingapparatus particularly suitable for the manufacture of pillow batts.

FIG. 21 is a schematic perspective view of the operation of across-lapping device useful for making tapered batts and in which thetraverse motion is at a right angle to the direction of movement of thecross-lapped batting.

FIG. 22 is a schematic plan view of the operation of a crosslappingdevice useful for making tapered batts and in which the traverse motionis at an acute angle to the direction of movement of the cross-lappedbatting.

FIG. 23 is a perspective view of the rolling of a tapered pillow battingmade by using the apparatus shown in FIG. 22, including a phantom viewof the crumpled core; and

FIG. 24 is a schematic diagram of an electric circuit for controllingthe cross-lapping operation illustrated in FIG. 21.

Referring to FIG. 1, a wide, spread web 9 of deregistered crimpedsubstantially parallel continuous filaments is supplied continuously toa pair of feed rolls 11 and 12, and drops down from the feed rolls intoa wide pivoted chute I3 made up of a pair of relatively closely spacedrigid panels or "doors" l4 and 16 which are mounted for oscillating,swinging, movement together about a pivotal axis 17. The web passesdownward between the doors l4 and 16 and is distributed, by theiroscillating action, back and forth across a continuously moving apron 18(which is preferably a driven endless belt) to form a cross-lappedbatting l9.

The wide web 9, which may be 50 inches wide for example, may be producedfrom a crimped tow 21 (FIG. 2) of a great many (e.g. 30,000) continuousfilaments, by passing the tow through a banding device 22, a threadedroll device 23 where the crimps of adjacent filaments are deregistered,and a series of air spreaders 24, after which the spread web passesbetween a pair of driven delivery rolls 26 (about which it makes an S-wrap). The foregoing procedure is described in detail in the previouslymentioned Belgian patent.

From the delivery rolls 26, the web passes upward to the rolls I1, 12,which rotate continuously at a predetermined constant and equal speedwhich is about the same (measured linearly) as the speed of the deliveryrolls 26. Preferably one of the feed rolls is axially driven while thesecond feed roll is pressed against the first roll and is frictionallysurface-driven thereby. The feed rolls may be arranged one above theother so that the web makes an S-wrap around the rolls (as shown inFIG. 1) or they may be arranged side-by-side.

The two doors 14 and 16 making up the chute 13 are supported at theirupper ends by brackets 28 and 29 arranged to pivot about the horizontalaxis 17, the mounting being such that the lower edges 31 and 32 of thesedoors can be brought together, when desired, to block the downwardmovement of tow between the doors. To this end one door 16 may be fixedto the brackets 28, 29, and the other door 14 may be pivotally connectedto the brackets, at pin 32a, for limited relative movement, so as toopen and close" the bottom of the chute. The unitary oscillatingmovement of the two doors may be effected in any suitable manner, as bymeans of a pneumatic or hydraulic cylinder 33, the flow of fluid to thecylinder being regularly reversed by a suitable valve 34 controlled inturn by adjustably mounted limit switches 36, 37 which are engaged bylaterally extending projections on the doors; thus, when the doors reachthe predetermined limit of their swing in either direction a limitswitch 36 or 37 is tripped by one of these projections, causing thepiston of the cylinder 33 to reverse its direction of movement. To openand close the bottom of the chute there may be another hydrauliccylinder 38 mounted on one of the doors and controlled by a presetadjustable timing switch (not shown).

The inner walls of the chute preferably have smooth surfaces over whichthe diaphanous web can slide easily without its filaments being caughtor snagged. Thus, the inner walls of the doors may be faced with sheets41 (FIG. 3) of flexible clear plastic, e.g. cellulose acetate,polyethylene, etc. To control the movement of the web, the side edges ofthe chute may be blocked off; thus the adjacent edges of the doors maybe joined by end pieces 42 (FIG. 9) of textile fabric or plastic film.

The use of the chute 13 makes it possible to produce battings whosewidth W (FIG. 4) is considerably greater than the traverse distance T ofthe lower ends of the doors. For example, battings about 84 inches widehave been produced readily even though the traverse distance is onlyabout 48 inches. This effect is particularly noticeable when the web isfed at a high speed. While not wishing to be bound by any particularexplanation, it is believed that this effect can be attributed to theair currents generated in the operation of the device. This isillustrated in FIGS. 5 and 6. FIG. 5 shows the position as the doorsstop at the extreme leftward limit of their swing; the arrow in thatFIG. 5 indicates the current of air generated by the rapid movement ofthe downwardly falling web 9. As indicated, there is little if anycontact between the web and the walls of the chute 13; thus, the righthand door, in pushing the web to the left, generally does not actdirectly on the web, but instead acts indirectly, through a cushion ofair. FIG. 6 shows the position just after the chute has started to swingto the right. As indicated by the lower arrow in FIG. 6, the previouslygenerated current of air is partially trapped under the diaphanousstill-falling web and causes it to billow out further to the left; theupper arrow in FIG. 6 indicates that the rightward swing of the chutegenerates another current of air that may also become partially trappedunder the web and aid in the billowing effect. Smoke tests show thateven after the chute has begun its rightward swing there is a definitegentle current of air moving to the left near the surface of the apronat the left edge of the apron. The billowing effect not only throws theweb further than the traverse distance but also causes it to spreadlaterally, so that it widens after it leaves the bottom of the chute asillustrated in FIG. 9.

Further movement of the chute toward the right overcomes the leftwardbillowing effect and causes the web to be laid down onto the apron, asillustrated in FIGS. 7 and 8.

For best results the web is supplied at a linear speed which isappreciably greater than the speed of the traverse. That is, in the timethat the traverse makes a complete cycle, travelling a distance equal to2T (see FIG. 4), there is supplied a length of web equal or greater than2W. The web speed is generally at least 10 percent greater than thetraverse speed, and preferably at least about 30 percent greater thanthe traverse speed.

It is within the scope of this invention to provide suitable bafflemeans to regulate and direct the currents of air so as to control thebillowing effect. Thus, there may be upright stationary baffles 44(FIGS. 10 and 11) flanking the edges of the bottom of the chute abovethe apron, or inclined stationary bafiles 46 (FIGS. 12 and 13)positioned to overlie the billowing web at each side of the traverse, orboth types of baffles may be used together. Also it is within thebroader scope of the invention to effect the cross-lapping by means ofalternately operating air streams, as by the use of two air headers 47,48 (FIGS. 14 and 15) each extending across the width of the-web 9 whichis being delivered from a non-traversing stationary chute 49, the airsupply to both headers being controlled (as by an adjustabletimer-operated switching valve) so that a controlled stream of air isblown first from one header 48 under the web 9 to cause it to billow outto one side, over the moving apron (FIG. 14) after which the air supplyto the header 48 is shut off and the air is furnished to header 47 tocause the web to billow out in the other direction (FIG. 15); thestationary chute 49 may be opened and closed at its bottom in the samemanner as previously indicated in the description of the moving chute13.

The invention also includes provision for cutting the web. In theembodiment illustrated in FIGS. 1 to 3, the bottom of the chute 13carries a web-cutting element adapted to be actuated at about the timethe bottom of the chute is closed. More particularly, an electricallyheated wire 51 is stretched between the projecting lower arms 52 of twobell cranks 53 mounted on, and at opposite sides of, one door, 16. Whenthe bottom of the chute is open the wire is positioned at the side ofthe door 16, away from the moving web. The upper arm 54 of one (or both)of the bell cranks 53 is pivoted to a rod 56 attached to the other door14 so that when the doors move towards each other, during the closing ofthe bottom of the chute, the hot wire is brought down into contact withthe web to sever the latter.

The manufacture of pillows is one important use for crosslapped battingsproduced from the spread webs. To form the stuffing of a pillow thecross-lapped material 19 may be rolled up to form a batt 58, as shown inFIG. 16, by means ofa driven roll 59 at the discharge end of the apron18. The device shown in FIGS. 1 to 3, previously discussed, isparticularly suitable for making pillow stuffings of novel andadvantageous construction. In one suitable cycle of manufacture of suchpillow stuffings the bottom of the chute is closed at the start of thecycle, thus cutting the moving web 9 and causing it to pile up in folds61 (FIG. 17) in the chute. The bottom of the chute is then opened sothat a wide mass, or wad, 62, of randomly folded web falls onto themoving apron 18, approximately along the center line of the apron. Thechute begins its swinging traverse movement and, for the remainder ofthe cycle, the web is therefore deposited in cross-lapped folds onto theapron. The bottom of the chute is then closed again, to cut the web andstart a new cycle. The movement of the apron carries the web material toa roll-up station where it is brought up against the continuously drivenwide roll 59 of relatively large diameter. There is thus formed arolled-up batt 63 (FIG. 19) having a randomly folded center 64 (therandomly folded material encounters the roll 59 before the cross-lappedportion) surrounded by cross-lapped layers 66, which is then stuffed,either manually or automatically, into an opened pillow tick, afterwhich the open end of the pillow tick is closed. as by sewing. The bestpillows are obtained when the general direction of the filaments of thecross-lapped layers 66 is longitudinal of the pillow. It will beunderstood that the filaments of the cross-lapped batt are not parallelto the long axis of the pillow, but are at an average angle of, forexample, in the range of about l030 on both sides of that axis. Forexample, the filaments of one layer of the crosslapped batt may be at anaverage angle of 20 positive to the long axis of the pillow while thefilaments of the next layer may be at an average angle of 20 negative tothat long axis. The pillows have a much lower tendency to matt than dopillows made of staple fiber batts; each cross-lapped layer ofcontinuous filaments resists penetration by the crossing continuousfilaments of the adjacent layers. With staple fibers there is moretendency for interpenetration of the layers. No bonding or stitching ofthe filaments or layers is needed in the manufacture of pillowsaccording to this invention.

In a typical l5-second cycle for the production of a pillow stuffingbatt weighing 20 ounces, the bottom of the chute is closed for 1 /2seconds and is open for 13% seconds while the web is supplied at aconstant rate; thus about 10 percent of the weight (i.e. 1 /2 divided by15) of the rolled-up batt will be randomly folded material. The presenceof the randomly folded material helps to give the pillow a desirablecenter crown.

The procedure described above yields pillows of excellent quality athigh production rates. The time interval between completion of therolling of one batt and the beginning of the rolling of the next battkeeps the batts clearly separate and thus facilitates the manual removalof the rolled-up batt from the apron, for insertion into a pillow.Without such batt separation, if the operators (handling thebatt-removal and pillow-stuffing operations) fall even slightly behindin their work in a high speed operation, two or more batts can be rolledtogether inadvertently.

Another procedure for getting good batt separation is illustratedschematically in FIG. 20. Here there are used, alternately, two traversepaths which are effectively disaligned in the direction of the lateralmotion of the cross-lapped material. In the embodiment shown in FIG. 20,a double width apron 71 is employed and the web 9 is deposited first onthe left half 72 of the apron, in a first traverse path, and then on itsright half 73, in a second traverse path. The chute 74 is made up of twoarticulated sections: a lower, rapid traverse section 76 (which isoperated in the same manner as the previously described chute 13, as bythe action of a hydraulic or pneumatic cylinder 79), and an uppersection 78 adapted to be moved, by the action ofa second cylinder 77,from an operating position (shown in solid lines) in which the lowersection is over the left half of the apron to a second operatingposition (shown in broken lines) in which the lower section is over theright half of the apron and vice versa. There are two sets of limitswitches 81, 82 and 83, 84 to control the rapid traverse movement at thetwo operating positions. There is a cutting device, preferably anelectrically heated wire 86 positioned at a level below the bottom ofthe chute 74 and above the middle of the apron 71, to sever the webtrailing from the chute during the change in operating position, withoutany provision being made for closing the bottom of the chute. The entireoperation may be controlled by any suitable timing apparatus (not shown)responsive, for example, to the number of rotations of the feed rolls11, 12. Thus, in one full cycle of operation, the timing apparatus mayactivate the left hand limit switches 81, 82 and rapid traverse cylinder79 so that the lower section 76 of the chute oscillates, thus laying acrosslapped batting; then the limit switches are deactivated, thepositioning cylinder 79 is activated to move the chute to the right(causing the web to be cut by the hot-wire) and the right hand limitswitches 83, 84 are activated so that a cross-lapped batting is laid onthe right hand side of the apron while the batting on the left hand sideis being rolled up and stuffed into a pillow. The positioning cylinder79 is then activated to move the chute to the left, cutting the webagain and starting the cycle anew. It will be appreciated that insteadof using a double width apron 71, two separate aprons corresponding toportions 72 and 73 may be employed and that these may move in the samedirection, as previously described, or in different (e.g. opposite)directions; in either case, the two traverse pathsare effectivelydisaligned in the direction of movement of the aprons.

Tapered batts may be produced by modifying the apparatus to make thecross-lapped folds of different lengths so that when the batting isrolled up its ends contain less material then the center. One method ofdoing this is illustrated in FIG. 21 in which the apparatus is the sameas shown in FIG. 1 except that four limit switches S1, S2, S3, S4 areemployed. These limit switches may be so connected that the wide swingof the chute is interrupted and reversed intermittently to produceadditional cross-lapped folds at the center portion of the swing. Forexample, in one construction, when the chute swings to the right itscontact with switch S3 causes it to reverse its direction before it hasmade its full rightward swing. It then contacts switch S2 which againreverses the direction of swing so that only a relatively narrow fold isproduced. The continued rightward swing of the chute brings it intocontact with switch S4 causing it to reverse its direction and swingleftward until it contacts switch S1, whereupon it swings to the rightagain.

In the construction illustrated in FIG. 24 of the drawing, each switchS1, S2, S3, S4 is part of a circuit C1, C2, C3, C4, respectively, eachcircuit being connected to a source of electric power P1, P2, P3 or P4and containing a solenoid S01, S02, S03 or $04 and a relay R1, R2, R3 orR4. In addition there are auxiliary switches A82 and A83 in circuits C2and C3, respectively.

In operation, when the chute swings to the right it trips switch S3 toclosed position and thus closes circuit C3, causing the solenoid S03 tomove the main chute-controlling valve 88 to its reverse position.Closing of circuit C3 also activates relay R3 which closes auxiliaryswitch A52 in circuit C2, making the latter ready for activation.

The movement of main valve 88 to its reverse position causes the chuteto swing leftward, tripping open the switch S3 (which does not affectthe position of the main valve 88).

Next the leftward swing of the chute closes the switch S2 closing thecircuit C2 and causing the solenoid S02 to move the main valve 88 to itsforward position, thus causing the chute to swing to the right. Closingof circuit C2 also actuates a relay R2 which opens an auxiliary switchAS3 of circuit C3, inactivating the latter.

The rightward swing of the chute first opens switch S2 (which openingdoes not affect the position of the main valve), then closes switch S3(which does not have any activating effect on circuit C3 since auxiliaryswitch A83 is open) and, finally, closes switch S4 which closes circuitC4, actuating solenoid S04 to move the main valve to its reverseposition, thus causing the chute to swing to the left. Closing ofcircuit C4 also actuates a relay R4 which opens an auxiliary switch A52in the circuit C2, inactivating the latter.

The resulting leftward swing of the chute first opens switch S4, thenopens switch S3 (neither of which now afiects the position of the mainvalve), then closes switch S2 (which does not have any activating effecton circuit C2 since auxiliary switch A82 is open) and, finally, closesswitch S1, thus closing circuit C1 and causing the solenoid S01 to movethe main valve 88 again to its forward position so that the chute iscaused to swing to the right. Closing of circuit C1 also actuates arelay R1 which closes the auxiliary switch A53 in circuit C3 making thelatter ready for activation.

The resulting rightward swing of the chute first opens switch S1, thenopens switch S2 (neither of which now affects the position of the mainswitch), then closes switch S3, closing circuit C3 and starting thecycle anew.

A very desirable type of tapered batt may also be attained by placingthe apron 18 so that its direction of movement M (FIG. 22) is at anacute angle (e.g. 30, 45 or 60) to the direction of traverse 0 of thechute 13 rather than at the 90 angle used in the previous illustrations.The resulting crosslapped batting is thinner at its edges (where thereare exposed corners 91) than at its center. The resulting tapered pillowbatt (otherwise produced in the same manner as illustrated for thenon-tapered batt) is shown in FIG. 23.

In one typical construction the chute is 5 feet wide and 4 feet high. Atthe top there is a tapered hopper-like section 92 (FIG. 1). The bottomof the chute is, for example, about a foot above the apron, which may beof smooth-surfaced rubber. The inner surfaces of the chute are coveredwith plastic film (e.g. polyethylene) and the sides of the chute(between the edges of the doors) are also covered with such film. Thedoors are straight and spaced, for example, 8 inches apart just belowthe hopper-like section 92. Best control of the cross-lapping operationhas thus far been obtained by the use of a chute of tapered construction(see, for example, FIG. 5 with the spacing between the doors at thelower, exit, end of the chute being about 1 to 2 inches when the bottomof the chute is open. For the pillow-making operation illustrated inFIGS. 17-19, 22 and 23, in which a wad of material is collected betweenthe doors, it is desirable-to have more space between the doors at thelower end of the chute so as to permit free and rapid downward passageof that wad; in this case the doors may be parallel, spaced about 8inches apart. In one typical pillow-making operation, the traversemovement of the bottom of the chute is about 14 inches and there are 64complete back-and-forth traverses per minute (making a total traversemovement of about 150 feet per minute) while the web travels at the rateof 200 feet per minute. In another example of a pillow-making operationthe speed of the rolls 1], 12 is about 260 feet per minute, the anglebetween the line of movement of the apron and the direction of traverseis 60, the speed of the apron is 55 feet per minute, the total traversecycle takes 20 seconds, during which the doors are closed for 3 secondsand then make 16 complete back-and-forth traverses, the tow used ispolyethylene terephthalate of 150,000 total denier, 5 denier perfilament, having an average of 12 crimps per inch and 30 percent crimp(i.e. ratio of straightened length to crimped length of the filament isl.3:l

By the use of this invention fine webs of considerable width (eg 50inches) can be cross-lapped effectively and continuously for substantialperiods of time at high speeds, using web delivery speeds of 600 feetper minute, 1,000 feet per minute or even higher. Generally the rate ofdeposition of the web material will be well over feet per minute andmore usually over 200 feet per minute.

In the finished pillows the weight of the batt will depend, of course,on the desired resilience and size of the pillow. For conventional sizesof pillows (e.g. pillows of area of about 500-600 square inches, such asa 20 inch by 26 inch pillow) the density of the batt before stuffing itinto the tick may be, for example, in the range of about one-half to 1%pounds per cubic foot. In stuffing it into the tick the batt iscompressed. Its density may increase by a factor of up to about 2 /2times.

The fine webs used as the feed material for making the batts in thepreferred form of the invention may be produced from tows of crimpedparallel continuous filaments by first opening the tow to disalign thecrimps of adjacent filaments and then spreading the tow, preferably withan air-spreading device, to produce the fine web. For the making ofpillows, the starting tow is preferably one whose filaments are ofpolyethylene terephthalate, but it is within the broad scope of theinvention to use other filaments, such as those made of other polyesters(e. g. the polyesters of terephthalic acid and other glycols such asdimethylol cyclohexane), linear superpolyamides (such as nylon 6 ornylon 66), polyacrylonitrile and copolymers of acrylonitrile, olefinicpolymers and copolymers, e.g. isotactic polypropylene, secondarycellulose acetate (of the usual acetyl content, e.g. about 5455 percentcalculated as acetic acid), other organic derivatives of cellulose suchas esters and/or ethers of cellulose, for example cellulose propionateand cellulose acetate propionate or the like, highly esterifiedcellulose containing less than 0.29 free hydroxyl groups peranhydroglucose unit such as cellulose tricetate, rayon (regeneratedcellulose), etc. The number of filaments of the starting tow can varywithin wide limits and may range up to as high as l,000,000, with adenier per filament as high as 25, e.g. l to 20, preferably about l-l0.The number of crimps per inch of tow may range up to as high as about80, but for most end products to be described herein about 3 to 30,preferably about 7 to 15, crimps per inch of starting tow are best.

The tow may be conveniently opened, to prepare it for the air spreadingsteps by subjecting it, while moving in a predetermined path, to adifferential gripping action between a plurality of points spaced fromone another both longitudinally and transversely of the path, so thatcertain laterally spaced sections of the tow are positively grippedrelative to other laterally spaced sections of the tow, alternating withthe said gripped sections, which are not gripped at all or are grippedat different relative points. In this manner there is produced, as afunction of the differential positive gripping of the tow, a relativeshifting of adjacent filaments longitudinally of the tow, whereby thecrimps are moved out of registry with one another. Preferably, althoughnot necessarily, the differential gripping action is such that arelative lateral displacement between adjacent filaments of the two isalso effected, so that the combination of two transverse filamentmovements brings about the complete opening ofthe tow.

The differential gripping action may be achieved by the provision of atleast one pair of rolls, one of which is smoothsurfaced and the other ofwhich is grooved over its entire periphery; if desired, there may be aplurality of such pairs of rolls arranged in tandem. On each groovedroll, the grooves and the ridges alternating therewith may extendobliquely or helically in opposite senses from its center to itsopposite ends. Thus, when the tow passes between the two rolls of anygiven pair of one grooved and one smooth-surfaced roll, some of the towsections are gripped between the peaks of the ridges of the grooved rolland the outer peripheral surface of the opposed smooth-surfaced roll,while other sections of the tow which are at that time located inregistry with the spaces between the ridges of the grooved roll are notgripped between the latter and the smooth-surfaced roll. Generally onlyone roll of each pair is positively driven while the other is yieldablybiased toward it and rotates due to the passing of the tow between therolls.

The tow-opening process is illustrated in U.S. Pat. Nos. 3,156,016 and3,032,829.

In the preferred method of spreading, the tow is passed through an airspreader in which the moving tow, in flattened condition, is confinedbetween parallel walls while streams of air or other suitable gas aredirected at the tow across its full width. Advantageously, the airspreading is effected in a plurality of stages in each of which the towis spread to a greater width than in the preceding stage. For bestresults the tow in any one stage is isolated from the effect of thefollowing stage as by passing the tow between stages firmly in contactwith a surface moving at a controlled rate, e.g. around and between apair of driven nip-defining rolls.

By air spreading it is possible to spread the tow readily, and veryevenly, to great widths to produce webs of extreme fineness, such aswebs containing less than about 500, e.g. filaments per inch of width,and in which the average air space per fil is appreciably greater thanthe diameter of the filaments. The average air space per fil is theaverage space between the filaments of the web measured on a line in theplane of the web, perpendicular to the longitudinal direction of thefilaments of the web, said space being calculated on the assumption thatall the filaments are arranged in a single plane, with no filamentscrossing other filaments. It may be calculated simply from a knowledgeof the average diameter of the filaments (D the width (w) of thesubstantially uniform web and the number of filaments (n) in said width,according to the formula: Average Air Space Per Pi! (w nD n.

Preferably the average air space per fil has a positive value, mostpreferably several times (eg 2, 5, 10 or more times) as great as theaverage filament diameter, and the density of the web is at most about 1ounce per square yard and most preferably well below 1 ounce per squareyard, e.g. one-tenth to one-fourth or one-half ounce per square yard.

The air spreaders themselves advantageously have airdelivery slits orother suitable openings in one or both of the parallel walls betweenwhich the tow passes, said slits leading from a plenum chamber suppliedwith air at constant pressure. In one highly effective constructionthere are a series of slits, each running in a direction transverse tothe direction of movement of the tow and so arranged that all portionsof the tow are subjected to the air streams from said slits. It has beenfound that even when the width of the air spreader is 8 feet or more,the tow spreads uniformly and the outer edges of the tow, where theresistance to the air would be expected to be less, attain substantiallythe same density as the central portions of the tow.

The pressure in the plenum chamber may vary, one suitable range beingabout 1 to 5 psig; higher pressures may be used, e.g. 100 psig, butthese are economically wasteful. The pressure in the tow-confining zone,between the parallel walls, is believed to be a little less thanatmospheric. When the air is blown straight at the face of the web, theair generally leaves the tow-confining zone from both ends of said zone.Little air is needed to expand the tow. Despite the fineness of thewebs, the walls of the tow-confining zones of the air spreaders need notbe correspondingly close together; thus very good results have beenobtained with tow-confining slots one-tenth inch in width.

In the preferred fine webs all the continuous filaments aresubstantially parallel; that is, they run in the same general direction,lengthwise of the web. However, when one does not look at the whole ofthe long length of any particular filament, but looks instead at theindividual crimps thereof, it will be seen that most portions of thefilament do not run in this general lengthwise direction but insteadzigzag back-and-forth across such general direction. The amplitude ofthe crimps is such that, for any particular filament, the portion of thecrimp at one side (hereafter termed the crest" of the crimp) overlapsone or more neighboring filaments while the portion of the crimp at theother side (hereafter termed the valley" of the crimp) overlaps one ormore of its neighboring filaments on said other side. This overlap helpsto give the webs their cohesiveness. For example, the filaments in theweb may have a crimp whose amplitude (from a median line running in thesame direction as the filament) is in the range of about one one hundredand twenty-eighth to three-sixteenths inch, said amplitude beingmeasured from said median line to the top of a crest, or to the bottomof a valley. Since there may, for example, be several hundred filamentsper inch of web width and since the crimps are not in registry, therewill be considerable overlapping of filaments in the web.

When one turns from an examination of the crimps and takes a somewhatlarger, though still relatively short, view of the portion of anyparticular filament which contains several crimps, and which may be forexample one-halfinch to several inches long, it will be found that theseportions are not perfectly parallel to the longitudinal direction of theweb, but make small angles therewith, which angles change in directionand magnitude along the length of the filament; generally these anglesare less than 20, although for very short portions (eig. one-half inchlong) the angle may be larger at times.

It is believed that the overlapping of the crimps and the overlappingdue to the presence of the angularly disposed short portions, justdescribed, contribute to the cohesiveness of the web so that, despiteits fineness, it can be readily handled as a unitary structure. Thedegree to which the individual filaments meander by virtue of thepresence of said crimps and angularly disposed short portions is not,however, very great; typically, the ratio of the straightened lengths ofthe individual filaments to the lengths of the same filaments in the webis less than about 1%: l and, preferably, greater than l.l:l, e.g. about1,211 to 1.4:1. This ratio may be measured by cutting a predeterminedlength of the web, removing the individual filaments of the cut portionand measuring their lengths while under a tension just sufficient toremove the crimp; the results are then expressed as the ratio betweenthe measured lengths of the individual filaments and said predeterminedcut length.

In specifying denier per filament and total denier, the number givenherein, with respect to tows and webs, is the denier for the filamentsprior to crimping, i.e. the weight of 9,000 meters of straightfilaments; the weight of 9,000 meters of crimped, unstraightenedfilaments or tow will naturally be greater than these values.

The fine webs are quite susceptible to snagging of individual continuousfilaments, particularly when the latter are of relatively strongmaterial such as polyethylene terephthalate. The previously describedair cushion resulting from the operation of the chute helps to avoidsuch snagging, especially when the chute doors and their edges havesmooth plastic surfaces as described above.

It is to be understood that the foregoing description is given merely byway of illustration, and that variations may be made therein withoutdeparting from the spirit of this invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A process for the production of a cross-lapped structure comprisingcontinuously feeding a longitudinally moving diaphanous, limp, cohesiveweb of crimped deregistered substantially parallel continuous filamentsinto a chute at least as wide as said web, moving said web downwardthrough said chute while oscillating the exit of said chute in oppositereciprocal directions at a predetermined rate to provide a predeterminedlinear speed of traverse of said exit, discharging the moving web fromthe chute onto a support while simultaneously aiding the traversing ofsaid web by means of outwardly moving gas currents between said web andsaid support which bellow said web to a widened condition and force theweb past the outer limits of the traverse of said exit at each end ofsaid traverse, the web linear downward speed being at least 10 percentgreater than the traverse speed, to thereby provide a cross-lappedstructure comprising said spread web in folded condition on saidsupport.

2. The process of claim 1 wherein the web is bellowed by air currentsgenerated by the oscillation of said chute.

3. Process as in claim 1 in which, during passage of the web through theexit portion of the chute, there is a cushion of air between the spreadweb and that wall of the chute which is moving toward said web.

1. A process for the production of a cross-lapped structure comprisingcontinuously feeding a longitudinally moving diaphanous, limp, cohesiveweb of crimped deregistered substantially parallel continuous filamentsinto a chute at least as wide as said web, moving said web downwardthrough said chute while oscillating the exit of said chute in oppositereciprocal directions at a predetermined rate to provide a predeterminedlinear speed of traverse of said exit, discharging the moving web fromthe chute onto a support while simultaneously aiding the traversing ofsaid web by means of outwardly moving gas currents between said web andsaid support which bellow said web to a widened condition and force theweb past the outer limits of the traverse of said exit at each end ofsaid traverse, the web linear downward speed being at least 10 percentgreater than the traverse speed, to thereby provide a cross-lappedstructure comprising said spread web in folded condition on saidsupport.
 2. The process of claim 1 wherein the web is bellowed by aircurrents generated by the oscillation of said chute.
 3. Process as inclaim 1 in which, during passage of the web through the exit portion ofthe chute, there is a cushion of air between the spread web and thatwall of the chute which is moving toward said web.